Synthesis Of Molybdenum Trioxide-Based Nanocomposite With High Gas Sensing Activity

Gas sensors are widely used to real-time detect harmful and explosive gases.Semiconductor gas sensors have gained special attention in fundamental science and practice for sensing harmful gases owing to the characteristics of low cost,high sensitivity,good stability and portability.MoO₃ is one of the greatest potential gas sensing materials among the transition metal oxides.Due to its unique lamellar structure,large specific surface area,electron transport along the axis and a large number of active sites,MoO₃ has become the focus of researches in recent years.This paper introduces the properties,applications,and advantages of MoO₃ using as gas sensing materials.In this study,a series of MoO₃-based nanoparticles,including MoO₃ nanobelts,MoO₃ nanosheets,MoO₃ nanospheres,MoO₃ microspheres,Au decorated MoO₃ nanobelts and In2O₃@MoO₃ core-shell nanocomposites were synthesized via a facile hydrothermal method and glycol-thermal method.The as-prepared products were characterized by XRD,SEM,TEM and XPS techniques,respectively.Finally,the gas sensing performances of the products were tested.The conclusions can be summarized as below:（1）By comparing the gas sensitivity performances of MoO₃ with different morphologies towards organic reductive gases,it was found that the gas sensitivity performance of MoO₃ nanobelts was better than the others.It shows optimal operating temperature（340℃）,excellent selectivity and high sensitivity to 100 ppm n-butylamine（81.2）.（2）A series of Au decorated MoO₃ nanobelts with different mass ratio of Au to MoO₃ were successfully prepared by in-situ reduction method.The results showed that the Au decoration can lead to the lower optimum working temperature than that of the original state MoO₃ nanobelts（decreased by about 80℃）.At the corresponding optimum working temperature,4 wt%Au/MoO₃ shows the best gas-sensing performance.Compared to the pure MoO₃ nanobelts,the gas sening performance to 100 ppm n-butylamine of Au decorated MoO₃ nanobelts increased 3.5 times.Au/MoO₃ nanobelts also performed high selectivity of n-butylamine,but the recovery time was extended accordingly.（3）In2O₃@MoO₃ core-shell nanocomposite with different In/Mo molar ratios were successfully prepared by a two-step hydrothermal method.The In2O₃@MoO₃ core-shell nanocomposites showed a significantly improvement in gas sensing performance compared with pure In2O₃ and pure MoO₃ microspheres due to the formation of heterojunction.In2O₃@MoO₃ core-shell nanocomposites with a molar ratio In/Mo of 1:5 showed the best gas sensitivity among the as-prepared nanocomposites.Compared with pure In2O₃,the optimal working temperature of the as-prepared In2O₃@MoO₃ core-shell nanocomposites decreased by 40℃,and the sensitivity was improved（Response was about 1.5 times of MoO₃ microspheres）.In2O₃@MoO₃ core-shell nanocomposites also exhibited high selectivity towards n-butylamine.